Western blotting is a very useful and common laboratory procedure. In the typical procedure, protein mixtures are separated on polyacrylamide gel into bands using an applied electric field. After the proteins are separated into bands, the separated bands are transferred to a membrane. After transfer, the separated proteins are probed with primary and secondary antibodies for detection. The detection can be accomplished via radioactivity, chemiluminescence, fluorescence, or absorbance. The most common detection method is chemiluminescence; however, in order to detect multiple analytes simultaneously, fluorescence has recently gained popularity.
After the separated protein bands are transferred to a membrane, it is often useful to show the separated bands, or to provide orientation or other experimental information from the membrane. Annotation and/or marking the position of protein standards for a Western blot membrane is typically done using a Sharpie® or other indelible fine tip felt pen. The film is overlaid and aligned atop the membrane and standard positions such as a protein ladder are noted on the film. With the use of imagers as a replacement to film, a need to mark the membrane directly is needed. Currently, other technologies for marking Western blot membranes utilize phosphorescent (Glow Writer®) or luminescent pens (Advansta®). Due to the various wash steps, it is often difficult to find suitable types of ink that will withstand the harsh wash steps.
In view of the foregoing, there is a need in the art for a pen to mark membranes and other solid surfaces which will be exposed to biological or chemical substrates and procedures. The present invention satisfies this and other needs.